A CD44 MONOCLONAL-ANTIBODY DIFFERENTIALLY REGULATES CD11A CD18 BINDING TO INTERCELLULAR-ADHESION MOLECULES CD54, CD102 AND CD50/

We have made a monoclonal anti-CD44 antibody which is able to activate the leukocyte integrin CDlla/CD18. Activated T cells strongly aggrega ted, and the aggregation was shown to be intercellular adhesion molecu le (ICAM)-1 (CD54) and ICAM-2 (CD102) dependent. Using purified ICAM c oated on plastic, only binding to ICAM-1 was increased by the CD44 ant ibody, whereas activation by phorbol ester increased binding to both I CAM-1 and ICAM-3. The binding to ICAM-2 was not affected by either tre atment. These findings show that the CD11a/CD18 integrin can be activa ted in a ligand-specific manner by engagement of CD44.